Bacterial community of oolitic carbonate sediments of the Bahamas Archipelago

The present study characterized bacterial communities associated with oolitic carbonate sediments from the Bahamas Archipelago, ranging from high-energy 'active' to lower energy 'non-active' and 'mat-stabilized' environments. Bacterial communities were analyzed using terminal restriction fragment length polymorphisms (TRFLP), clone analyses of the 16S rRNA gene, confocal laser scanning microscopy (CLSM) and the quantitative phenol-sulfuric acid assay for extracellular polymeric substances (EPS). Confocal imaging of oolitic grains stained with cyanine dye-conjugated lectin and EPS quantification demonstrated that all 3 environments harbored attached biofilm communities, but densities increased from the active to the mat-stabilized environment. Bacterial communities associated with all 3 settings were highly diverse and dominated by Proteobacteria (50 to 61%). Analysis of similarity (ANOSIM) and similarity percentages (SIMPER) revealed significant differences among the 3 environments in the relative abundance of Proteobacteria, Planctomycetes, Cyanobacteria, Chlorobi, and Deinococcus-Thermus. Bacterial primary production in the active shoal environment was associated with Rhodobacteraceae, Ectothiorhodospiraceae, and Chlorobi, whereas the lower energy environments appear to harbor a more complex consortium of aerobic photoautotrophs and anaerobic/aerobic anoxygenic phototrophs. The ubiquitousness of photosynthetizers, along with the presence of aerobic/anaerobic heterotrophic microbes (e.g. denitrifiers, sulfate-reducers, biofilm producers/degraders) and the gradient increase in biofilm production on ooid grains from active to mat-stabilized environments, support the potential involvement of these communities in biomineralization and carbonate precipitation.